338 MIDDLEMISS : KANGRA EARTHQUAKE 



isoseists, in the case of the Kangra area, was more nearly coincident 

 with that of the reversed fault between the younger Siwalik conglome- 

 rate and the older sandstones than with the main-boundary itself. The 

 evidence for the case at Dehra Dun was not, however, sufficiently con- 

 clusive, inasmuch as the two boundary faults run very near together 

 at that place. 



Another feature of •importance is the arc-like curve, convex to the 

 S. W., which the Himalayan range presents to the 

 Gangetic plain. It may undoubtedly be regarded 

 as having gradually resulted from the constant reshaping of that margin 

 by overfolding and faulting. The more marginal the rocks that are 

 involved, the more perfect is the alignment of that curve in all its sim- 

 plicity : whilst all the areas like the inner side of the Kangra valley and 

 Dehra Dun which are farthest away from that margin are those, which 

 show variations from that curve, and must have been places where special 

 local conditions have offered a temporary resistance to the normal onward 

 march of those regular waves of flexure. So long as no exceptional 

 local resistance of this kind interfered, one might be justified in conceiv- 

 ing the regular progression of these folds as happening smoothly and 

 without serious shock, but elsewhere at such centres of complexity we 

 might very well see cause for a struggle of opposing local and general 

 forces which might end in something catastrophic. 



These centres of complexity are the places signalised by thick depo- 

 sits of Upper Siwalik conglomerate. Their presumed deposition from 

 torrential rivers of commensurate magnitude with their similarly situated 

 descendants, the Beas and Ganges of to-day, and the fact of their 

 great thickness and rapid accumulation suggest a disturbing feature of 

 no small magnitude. On the principle of isostasy their continued 

 deposition must have been accompanied by a downward sinking of the 

 Dun areas which would tend to deflect arid upset the orderly southerly 

 march of the Himalayan arc folds. 



Summarising, we may say that the following features appertaining 

 to the geological, structural and orographic surroundings strike one as 



